Clare Nicholls's brother, Simon Nicholls, 24, was told he will serve at least 25 years for his part in the prolonged and agonising killing of vulnerable Andrew Gardner, 35.
A jury at Teesside Crown Court heard two weeks of graphic evidence about how the trio inflicted scores of injuries over months on the helpless Mr Gardner, who was also suffering blood poisoning and possible malnutrition when he died at their home in Chilton, County Durham, in March last year.
Judge Peter Fox, the Recorder of Middlesbrough, said most people who heard the evidence would describe the killing as "sadistic".
Clare Nicholls was the leader, and had a "deeply entrenched personality disorder".
The judge said: "In my judgment this prolonged killing was one of a particularly high degree of seriousness in the whole spectrum of murder."
Nicholls did not react when the minimum term was read out.
The judge said she was a "dreadful example" to her children who witnessed her violence.
Simon Nicholls's part in the killing was "lesser", yet was still "very serious".
Judge Fox added: "Knowing full well what your sister was doing to this man, you repeatedly were the enforcer, stepping in cruelly when he sought to resist or avoid her attacks."
He said Mr Gardner "died a slow and excruciatingly painful death".
"In the weeks prior to his demise on Friday March 13 last year, he was cruelly tortured and subjected to an appalling catalogue of attacks which not only caused him acute pain in so many ways at your hands, but also dreadful humiliation.
"In your sometimes different but sometimes joint ways, you each contributed not only to the breaking of his body, but also his spirit.
"In his final days that he must have spent prone or leaning against a wall, he was deprived of all human dignity."
Mr Gardner's mother Jean branded Clare Nicholls "evil" and said her family would never get over their loss.
"To be told that Andrew was dead was horrible and I knew there was something wrong straightaway," she said.
"He was someone who would simply walk away from trouble. To listen to the details of how he died and the suffering he went through was beyond belief.
"The thoughts of what went on at the hands and direction of that evil woman has left me with nightmares that will probably never go away.
"Andrew was a pleasant, caring, loving lad who kept out of trouble and was never violent to anyone.
"It has hurt being here. It has hurt watching her giving evidence, so much so I had to go out of the courtroom. I knew she was lying.
"It's unspeakable what she and the others did. You don't do that to another human being.
"They have turned our family's lives upside down and left us empty shells.
"I called them evil to their faces in court, but it hurt even more to see their smug reaction.
"No matter how long they are behind bars, the hurt they caused will never go away. It will be with me and my family for ever."
Detective Chief Inspector Mick Nail, who led the murder investigation, described Mr Gardner's murder as "the worst case of violence Durham Constabulary has had to investigate".
"To say it was been an extreme form of 'domestic abuse' is, sadly, an understatement," he said.
"The injuries that Andrew Gardner suffered could well have been inflicted by medieval torturers.
"Clare Nicholls is, without doubt, an extremely violent, manipulative, evil woman with no conscience.
"She led and orchestrated the abuse and degradation of Andrew and topped his suffering with humiliation."
The detective said this was made worse by the fact that Nicholls involved children in the torture.
"The jurors who sat on this trial were visibly shocked by what went on and I have no doubt the memories of what they were told will stay with them for a long time," he said.
"They saw through her lies and the sentence today will allow Nicholls plenty of time to contemplate on the consequences of her actions."
Rachel Masters, a Crown Advocate for the Crown Prosecution Service in County Durham, said: "Andrew Gardner suffered a painful and torturous death.
"The level of violence was extreme and his body could only put up with so much.
"These were not strangers, but people he knew and trusted, including the mother of his child, taking sadistic gratification from inflicting pain and suffering.
"They spurred one another on over a number of weeks, until ultimately they took Andrew's life."
Clare Nicholls' on-off boyfriend, Steven Martin, 44, will be sentenced next month, to allow for psychiatric reports to be prepared.
During the three-week trial, the jury heard that he joined in the attacks, and branded Mr Gardner with a cigarette lighter.
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